Multiple push button switch speed control system

ABSTRACT

A speed control system for a universal electric motor wherein field windings on one side of the armature are permuted by contacts of a multiple push button switch into a predetermined number of different series and parallel interconnections to achieve a maximum number of significantly different motor operating speeds with a minimum number of switch contacts. The number of speeds thus available is preferably doubled by selectively switching an additional diode and field winding into the field circuit, and a series switch contact is further provided in this circuit to interrupt current flow therein while the winding interconnections are being permuted to reduce the maximum current carried by the permutation switch contacts.

[451 July 18, 1972 [54] MULTIPLE PUSH BU'ITON SWITCH SPEED CONTROLSYSTEM [72] Inventors: Roy L. Swanke, Newington; Gordon H.

Raymond, Southington, both of Conn.

Dynamic Corporation of America, New Hartford, Conn,

22 Filed: April 24, 1970 21 Appl.No.:'31,803

[73] Assignee:

Related U.S. Application Data [62] Division of Ser. No, 766,280, Oct. 9,1968, abandoned.

[56] References Cited UNITED STATES PATENTS 2,482,513 9/1949 Rossignol..3i8/252 3,422,330 1/1969 Swanke ..3l8/305 3,493,833 2/1970 Swanke.........318/252 3,286,150 11/1966 Wilson ....318/245 2,482,513 9/1949Rossignol... ....318/252 3,283,227 11/1966 Ulinsky 318/252 PrimaryExaminer-Hemard A. Gilheany Assistant Examiner-Thomas LangerArtorneyHarbaugh and Thomas [5 7] ABSTRACT A speed control system for auniversal electric motor wherein field windings on one side of thearmature are permuted by contacts of a multiple push button switch intoa predetermined number of different series and parallel interconnectionsto achieve a maximum number of significantly different motor operatingspeeds with a minimum number of switch contacts. The number of speedsthus available is preferably doubled by selectively switching anadditional diode and field winding into the field circuit, and a seriesswitch contact is further provided in this circuit to interrupt currentflow therein while the winding interconnections are being permuted toreduce the maximum current carried by the permutation switch contacts.

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INVENTORS ROY L. SWANKE GORDON H. RAYMOND Ww I %M AT T'YJPATENTEDJUHBIQYZ 3.67835? SHEET u 0F 4 lNVENTORS ROY L. SWANKE GORDON H.RAYMOND ATT'YS MULTIPLE PUSH BUTTON SWITCH SPEED CONTROL SYSTEM CROSSREFERENCES TO RELATED APPLICATIONS:

Swanke, U.S. Pat. No. 3,493,833

Bull, U.S. Pat. No. 3,440,438

This application is a division of application, Ser. No. 766,280, nowabandoned, of which Ser. No. 63,511 is a continuation-in-part.

BACKGROUND OF THE INVENTION With increasing knowledge and research inlaboratories and in the field of food and drink preparation, the needfor greater ranges of fixed agitator speeds is becoming increasinglyimportant in formulas, receipes,timing and volumes for the best resultswhen ingredients are being comrninuted, mixed or blended. Factors suchas particle size, aeration, fluidity and overrun are not only concernedwith timing but also a wide selection of accurately controlled fixedspeeds.

Multiple push button switches have been used in great numbers for thecontrol of electrical appliances and are increasingly used in home andindustry with demands for a greater number of push buttons for quicklyselecting fixed speeds as distinguished from an infinitely variablecontrol that must be adjusted. Adequate space within an appliancehousing for multiple switches is a problem as well as minimizing theincreasing cost of the greater versatility that is desired.

Increase of speed selections along with minimization of spacerequirements and reduction of costs are objects of the invention inwhich selector switches only carry current, the field coils are multiplein number on each field pole, are simultaneously wound directly on eachcore in one winding operation and are of different gage sizes andresistances.

The speed selection is related to various combinations of coils withvarious combinations of switches selected by push buttons in which theselection is completed and terminated without any current passingthrough them. Furthermore, the selection of speeds is doubled withoutany additional switches, each switch combination serving for two or morespeeds.

The present invention embodies a multiplepush button switch assemblyhaving movable permutation sliders each provided with a series ofnotches arranged along one edge and having cams engaged by respectivepush rodsfor movement between two terminal positions. One or moresliders are activated by each button and have cams arranged in recessesalong their other edge permuted to actuate movable contacts ofparticular switches according to predetermined pattems' for each buttonpressed. The switches that are actuated connect individualized fieldcoil windings of a universal motor selectively in series or parallel, orboth, to change the efiective resistance of the motor field for fixedmotor speed selection purposes.

In the present invention, however, as described in said Swankeapplication, the difi'erent speed selections that are available with agiven number of switch patterns are doubled. This is accomplishedautomatically in the present invention by another series of buttonsincreasing the overall field resistance and changing the appliedelectrical potential as controlled by the same switches in identicalpatterns.

Moreover, the housing space required for the switching is furtherreduced by a time sequence switching in which, at a savings in cost, theswitches that selectively control the field resistance and appliedelectrical potential are selectively closed first and opened last withrespect to the operation of a heavy dutymain switch which makes andbreaks the electrical current circuit. The selective switches arelightly built as rated to merely conduct current and do not needexpensive contact elements as long as they are nonoxidizing or have awiping action, or both, to provide excellent electrical conductivity.The switch for closing and opening the circuit can either be backto-backsilicon controlled recu'fiers that share the circuit load with a lightlybuilt mechanical switch as described in the Bull application or a heavyduty mechanical switch that is readily embodied in multiple slider gangswitch as described herein to make and break as well as carry the fullload itself.

Accordingly, the buttons and sliders are sequentially coordinated toactuate the permuted speed control switches to open first and close lastand the main switch to open last and close first with respect theretoeach time the control switches are set or reset by push buttons.

The rectifier switch is either opened or closed through intermediateelements that are alternately reciprocated by the buttons of thediiferent pairs at the time the speed control switches and the mainswitch are being sequentially controlled by any button that is beingactuated to provide the desired permutation pattern of speed controlswitches.

One of the objects of the present invention is to enable greater freedomof choice of switch combinations for well selected fixed speeds in thatall speed control switches are not required to be in OFF" position whenthe motor is idle thereby providing greater versatility with or withouta timer being present having a switch.

Another object of the invention is to provide particularized selectionsof different field coils not only for series connection but also forparallel connection on either side or both sides of a serially connectedarmature.

The invention is also characterized by the number of switches used forspeed control, being less than one-fourth the number of different fixedspeeds mathematically available with a multiple field coil motor havingfour or more field coil leads on either or both sides of the armature.

The invention also provides at least twice as many speed selectorbuttons as there are control switches for different fixed speeds.

The invention also contemplates a basic switch construction that can beprovided with a particular number of control push buttons for a setnumber of fixed speeds or twice the number of push buttons for doublethe number of speeds without increasing the number of control switches.

The invention provides for a time dimensional sequential switchoperation in which only one switch need be rated for making and breakingthe power current.

Other objects and advantages of the invention will appear more fullyfrom the following description and from the accompanying drawings, inwhich similar characters of reference indicate similar parts throughoutthe several views with or without additional suffix identifications.

FIG. 1 is a side elevational view of a multiple push button switchembodying l5 push buttons and eight switches;

FIG. 2 is a top plan view of the speed selection multiplier attachmentfor the switch shown in FIG. 1 with the buttons removed;

FIG. 3 is an end elevational view of the switch shown in FIGS. 1 and 2;

FIG. 4 is a sectional view taken on line 4-4 in FIG. 2 as oriented withrespect to a mounting plate;

FIG. 5 is an electrical schematic of a representative circuit used inthe present invention;

FIG. 6 is a graph of the possible fixed speed selections available withthe circuit in the present invention utilizing six speed controlswitches;

FIG. 7 is a chart of sixfixed speed selections showing the permutationof switches with respect thereto controlled by selective push buttonactuation;

FIG. 8 and 9 are enlarged fragmentary side elevational views of thediode sliders in their diode energizing positions;

FIG. 10 is a fragmentary side elevational view of the main switch sliderin OFF position;

FIG. 11 is a side elevational view of a representative speed or selectorswitch;

FIGS. 12 and 13 are fragmentary side elevational views of the slider inFIG. 8 in alternate positions in combination with guide plates;

FIG. 14 is a side elevational view showing the elements of FIG. 13mounted in a housing;

FIG. 15 is a cross-sectional view similar to FIG. 4 of anotherembodiment of the invention;

FIGS. 16 and 17 are end views partly in section through the housingshown in FIG. 14 shown transversely paired push rods in resting positionand actuated position respectively; and

FIG. 18 is a perspective view of the push rod' employed in theembodiment shown in FIG. 14.

The construction of switch shown in FIGS. 1 to 4 is somewhatconventional in that it has a hollow elongated housing 12 molded ofsuitable insulating material having an upright central portion 14defining a slider chamber having mounting holes 15 and 16 whose sidewalls 17 support the sliders 32 as a group for relative longitudinalreciprocation. Opposing vertical grooves 20 in the side walls 17 receivepush rods 22 in guided relation which extend through narrow slots 24 inthe top 26 of the central portion 14 for purposes of selectiveactuation. The switches 30 actuated by the sliders 32 are located belowthe sliders and comprise a row of stationary terminals 34 havingdownwardly facing fixed contact areas along one side of the slidechamber 16 and a row of fixed terminals 36 along the other sideresiliently supporting one end of bridging conductors 38 whose otherends provide contact areas resiliently urged to close against thestationary contacts 34 in an upward direction. A flat cover plate 40 ofinsulating material is secured to the housing 12 by suitable means toclose the switch chamber with sufficient clearance to pemiit operationof the bridging conductors 38.

The sliders 32 of the embodiment shown in FIG. 4 are four in number, aremade of insulating phenolic board and are supported by spaced extensions42 (FIG. 11) along their lower edges slidably bearing against the coverplate 40 to carry the downward thrust of the push rods 22 against them.Between successive extensions 42 the lower edges of the sliders haverecesses 44 at each switch station or conductor 38 and are provided withvarious shapes to operate or not operate the conductors as theirpermutation requires. Generally, if the conductor is to be actuated at aparticular recess, there are provided a high dwell 46 and a low dwell 48separated by a cam incline 50 which either closes the switch or opens itdepending upon the relative location of the conductor and the directionof movement of the slider when actuated. Thus, when a switch 30 is openthe corresponding recesses 44 of the four sliders are arranged so withrespect to the switch conductors 38 that one or more high dwells 46 ofthose present engages the conductor to hold the switch open in adownward direction, and when a switch is closed the low dwells 48 of allfour recesses 44 at that station coincide to permit the resilientconductor 38 to rise and close the contacts.

For permutation of the sliders 32 and thereby the switch closures, theupper edges of the sliders have notches 52 for each push rod 22. Thenotches generally define a vertical side 54 and a side inclined theretoto provide an actuated cam surface 56. In some embodiments the verticalsides have horizontally directed tickler V-cams 58 (FIGS. 8, 10)adjacent the top to partially retract the slider 32 by an actuated pushrod preliminary to returning the slider to its advanced position byfinal engagement of the push rod against the inclined cam 56. The apices60 of the recess sides have a contour matching the shape of the lowerend of the push rods 22. Preferably this shape is rounded and such caneither have a small radius for the edge 62 of the rod or have a largerradius as at 64 to mate with the curled enlarged edge portion 66 of thepush rod.

The upper ends 68 (FIG. 4) of the push rods 22 where they extend abovethe openings 24 have a substantial width to be alternately actuated aslater described by two adjacent plungers 70.

For this purpose a main mounting bracket 72 (FIGS. 2 and 4) is providedhaving a central aperture 74 received over the upstanding controlportion 14 as provided at both ends with upstanding ears 75 having pivotholes 76 therein. Transversely elongated slots 78 are provided outsideof the ears to accommodate the endmost push rods projecting from theswitch housing. Beyond these slots mounting holes 80 are provided formounting the assembly on the housing 10 and on an appliance.

The sides 82 of the bracket 72 extend laterally beyond the centralportion 14 where they are apertured as at 84 directly opposite each pushrod opening 24 and then marginally turned down to form a reinforcingflange 86 that also serves as a guide element for the plungers 70 inconjunction with the apertures 84.

Pivotally mounted to the arms 75 as by rivet pins 88 is a rectangularframe 90 whose sides 92 are spaced vertically and horizontally adistance outwardly of and parallel to the flanges 86 with a tab 94 atone comer (FIG. 2). A single-pole singlethrow (SPST) slide switch 96 ismounted by an auxillary bracket 98 on the flange side 82 of the mainbracket 72 with its button 100 reciprocated by a link 102 pivotallysecured to the tab 94 as the frame 90 rocks about the pivot pins 88.

The switch unit 10 thus described is mounted either on a decora-tiveplate 104, (FIGS. 1 and 4) or upon the wall of an appliance with spacers106 locating the upper ends of the push rods a slight distancetherefrom. Screws 107 extend through the plate 104, the spacers 106,mounting holes 80 and are threaded into the mounting holes 15 to securethe switch unit in place.

Whether it be a decorative plate or a wall, slots 108 are providedtherein for reciprocably supporting push buttons 110 therethrough onopposite sides of the push rods 22 and in alignment with the apertures84 in the mounting bracket 72. The cross-shaped plungers 70 provided,each have a slot 114 in its leg 116 receiving the flange 86 while one ofthe bifur- I cated portions 118 is received in the apertures 84. Theupper end 120 is split to be resiliently received in the button 110. Onearm 21 engages the bottom of the plate 104 on its upper edge and on itslower edge drives the side 92 of the frame 90. The other arm 23 extendsinto overlapping relationship with one-half of the push rod 22 and has alaterally extending ear 25, preferably reversely bent, to engage theupper end of the push rod 22 in encompassing relationship. Downwardmovement of any push button 110 and plunger 112 actuates the push rod 22and rocks that side of the frame 90 downwardly to operate the slideswitch 96 accordingly. Light compression springs 18 are mounted on theother bifurcated portion 19 to return the plunger.

The leads from slide switch (1) (FIG. 5) are connected in series betweenthe switch unit 10 and one side L of the AC power line. A diode 27 isconnected between the terminals 29 of the switch.

In operation, alternate actuation of cross-paired buttons 110 rock theframe 90, actuate the same push rod 22 but alternately actuate the slideswitch 96 to piece the half-wave rectifier 127 in or out of the circuit.This operation of the slide switch 96 doubles the number of speedscontrolled by the multi-push-button switch 10.

Referring now to the embodiment shown in FIGS. 8 to 18 the diodeswitching operation is incorporated in sliders. In this embodiment theslider chamber 16A (FIG. 15) and the central portion 14A are wider toaccommodate seven sliders 32A and two guide plates 31 whose salientfeatures are shown in FIGS. 8-14. In this embodiment two cross-pairedpush rods 22A are provided for each station as received in slidingsupported relation in two axially aligned slots 24A provided in the topof the central portion 14A.

Each of the cross-paired push rods 22A operates in the same notches 52of the sliders 32a and for this purpose are constructed as shown inFIGS. 16-18. All are identical for inventory purposes and each comprisesan L-shaped sheet metal stamping 35 notched at the top edge to receivethe push buttons 110 and rounded along the bottom edge to slidablyengage the respective sliders in their respective notches. The toeportion 35 of the foot portion is flat so that two of them cooperateface-to-face (FIG. 10) while the heel portion 37 is enlarged by a curl66 of metal to move in guided relation in the groove guideways 20 in thewall of the chamber 16A. A U- shaped push rod 41 may be used for theSTOP button and be provided with a rounded enlarged edge 66 extendingthe full length of the lower edge since the STOP button is single and issecured to both vertical legs 22M of the push rod 41.

In the particular embodiment illustrated there are two more switches 30than there are switches devoted to'fixed speed control. These switchesare the diode switch 30D which is conjointly controlled by the speedcontrol buttons and the main switch 30M controlled by the STOP button.

The diode sliders 32D are two in number, one located against one wall 17of the slider chamber 16A and the other against the other wall 17 wherethey are disposed to be acted upon by the enlarged portions 66 of thepush rods 22A. Holding them in place are two rectangular guide plates 31(FIG. whose four marginal edges (FIG. 14) engage the end walls 178 ofthe chamber 16A against longitudinal displacement while the top andbottom walls 17T and 17B provide for firmness of support.

The upper edges of the guide plates are vertically notched to provideguideways 43 matching the groove guideways 20 in the chamber walls andlikewise accommodate in guided relationship the enlargements 66 on thepush rods 22A, 22D and 22M. Along their lower edges the guide plates arerecessed as at 45 to guide the resilient conductors 38 and 38M of theswitches in their vertical movement and support them against lateraldisplacement when cam actuated. In this connection the conductors 38,being made of spring bronze metal strip are formed by the female formingdie being located on the convex side of the U-shaped cross section whichis shown as ultimately formed. This provides smoothly rounded edgesengaging the walls of the guide recesses 45.

Between the guide plates are located the sliders 32$ for the speedcontrol switches 30 and the slider 32M for the main switch. As a matterof convenience, the main switch slider is in the middle of the foursliders 32$ for intimate operational accuracy in the performance of theswitches 30.

In this embodiment a characteristic speed control slider 328 is shown inits entirety in FIG. 11, it being well known as already mentioned howthe contours of the respective recesses 44 may be arranged on all fourspeed controls sliders for permutation of six switches for seven speeds.The significant end portions of the other three sliders 32D and 32M forthe diode sliders and main switch slider respectively, are shownenlarged for easier viewing, the remaining recesses, now shown, beingduplicates of the last recess shown towards the lefi as viewed.

For a better understanding of the description which follows it may bewell to note at this time that the diode switch 30D is preferably openedalong with the main switch 30M when the STOP button is pressed. Both themain switch and permutated speed switches 30 are closed when any speedpush button is pressed. If the push button pressed in the row of buttonson the side of the diode 2 sliders, the diode switch is left open forlow speeds involving half-wave rectification. If the pushbutton pressedis in the other row of buttons on the side of the diode 1 slider, thenthe diode switch is closed to shunt the diode for high speeds at thefull wave electrical potential. The diode switch is opened again when alow speed push button is pressed, namely, the diode 2 sliders. The twosliders 32D and 32D,,, move simultaneously when either is actuated. Oneadditional relationship is also preferred, namely, that the main switchslider is at least momentarily opened during the midpoint movement ofthe diode sliders whenever any speed button is pressed.

With respect to simultaneous movement of the diode sliders only thediode switch sliders 32D and 32D,. operate the diode switch 30D and theyhave recesses 44D for this purpose in which there are high and lowdwells at only'the diode switch station. The arrangement of those dwellsdepends upon the cooperative movement between the sliders. The diodesliders may be operated upon the basic theory of relative reciprocationfor the diode switch actuation as described previously with the firstembodiment, or upon conjoint movement in the same direction each timeeither one is moved. In the former, dwell contouring in the diode switchrecesses are symmetrical, in the latter they are identical with respectto each other as shown. On the other hand, in the former, the actuateddiode slider notches 52D are identical in being inclined in the samedirection while in the latter they are symmetrical with respect to eachother in being inclined in opposite directions as shown. For purposes ofdescription, the latter is illustrated wherein the diode switch slidersoperate together in the same direction of movement.

Both diode sliders have recesses 44D at the station of the diode switch30D in which the high dwells 46 open the switch at one limit of theirmovement in one direction and the low dwells 48 permit the diode switchto close when both sliders are disposed at the other limit of themovement in the opposite direction. Although the notches $2M in thediode sliders for the STOP push rod 22M may be provided with fullclearance for the main switch 30M, it is desired that the diode switchbe opened with the opening of the main switch even though the diode isstill in the circuit becausethe load of camrning open the diode switchis carried by the STOP button every time that the STOP button isactuated.

Otherwise all of the speed control sliders have recesses 44 that clearthe diode switch. It is only through the notches 52D provide on thediode sliders for actuation by the speed control push rods 22A that thediode switch is opened or closed. In fact, the diode sliders and themain switch slider 32M, if it is OFF, are actuated each time a button ispushed.

For this purpose the two diode sliders are rigidly cross-connected attheir ends by rivets 47 and spacers 49 while the ends of the othersliders and the guide plates are slotted as at 51 to receive in mutuallysupporting relationship and accommodate the movement of thecross-connecting members 47. The spacers not only move the diode sliders32D as a unit but also hold the stick of sliders 32 and guide plates inassembled relationship as a unitary subassembly that is easy to make andhandle in production.

The spacers comprise a sleeve 53 (FIG. 15) flared at opposite ends toprovide squaring flanges 55 engaging the facing surfaces of the diodesliders and a sleeve rivet 57 with widely flared heads 59 to providesquaring flanges 49 engaging the remote faces of the diode sliders 32D.The cross-connectors move both sliders as a unit. However, when oneslider is positively moved, there is very little load transmittedthrough the connectors to move the other slider. They maintain a squaredrelation for simultaneous movement because both sliders are performingthe same work at the same time to accomplish the same result. Theirdiode switch recesses are identical and whichever one is actuated, itdirectly carries the load encountered by its movement.

The operation from the description thus far is one in which actuation-ofthe STOP push rod 225' places the diode sliders 32D in the positionsshown withthe high dwells 46 holding the switch 30D open. If a low speedbutton is pressed, the diode sliders remain in the positions shown withthe low dwells 48 permitting the shunting diode switch "OPEN. If a highspeed button is pressed, both diode sliders 32D are moved to release thediode switch connection to its closed position. The release-to-closeeffort is a slight working effort and is carried essentially by theslider that is being directly actuated which preferably is the onelocated nearest to the free end of the movable switch connector.Thereafter, when a low speed button is pressed for lower speed, the loadof opening the diode connector switch is carried directly by the diodeslider being actuated. As already mentioned, this is also true of themain switch slider at its diode switch recess.

Thus, with actuation of either one of a plurality of pairs of buttonspermutating the speed control switches, the selection of a particularbutton of each pair provides a fixed speed that is independent of allother speeds and particularly different from the speeds established bythe actuation of the other buttons of each pair. Thereby, the speedselection is doubled with the same number of switches plus one that isrelated to a diode 27. It is appreciated that the actuation of any speedbutton will close the main switch while the stop button opens the mainswitch regardless of whether the other speed selection switches or diodeswitch remains closed or open.

TIME DIMENSIONAL SEQUENCE SWITCH OPERATIONS Both the diode and speedcontrol sliders (FIGS. 8, 9 and 10) have long switch closing low dwells48D in their recesses 44D and short switch opening high dwells 46D attheir pertinent recess stations on the sliders. These time the openingand the closing of the switches in approximately the upper half of theeffective movement of the push buttons. The main switch slider 32M onthe other hand has a short low dwell 48M for switch-closing and a longhigh dwell 46M for switch-opening, timed for opening and closing themain switch in approximately the lower half of the effective movement ofthe push buttons. This is operated by either set of buttons inconjunction with the speed control sliders.

This relates to the sequential switch operation heretofore mentioned.For this purpose speed selector and diode switches are constructed for arating of merely conducting current since the invention contemplatesthat they will not make or break the electrical current. They merelyconduct it. The

speed control switch permutations are completed and switches actuatedeither to open or to close while the main switch is open, after whichthe main switch is closed.

More particularly, in accomplishing this one of the novelcharacteristics of the four speed sliders and the two diode sliders isthat wherever one of their recesses has two vertically spaced dwells, 46and 48, the cam incline 50 between them is closer to the high dwell endof the recess. Moreover, since the diode sliders 32D are actuated eachtime a push button is pressed, a snap action protuberance 61 is providedin the upper portion of each of their main switch recesses 44M whichopens the main switch each time during the midway portion of the travelof a button that is pressed.

In event buttons happen to be pressed in a succession which does notchange the diode sliders, the vertical sides of all of the diode slidernotches 52 are provided with horizontally extending tickler cams 58 thatare engaged and momentarily displaced by the enlarged rounded bottom 66of the push rods 32A. When one of these cams is engaged during adownward or upward push rod thrust it is moved by the enlarged end ofthe push-rod to clear it. This moves the slider far enough for the snapaction protuberances 61 to open the main switch 30M during the time thatthe other switch permutations are being set or reset. This occursregardless of which speed selection button is pressed if the diodeslider involved is already in the ultimate position intended. If thediode slider 32D involved is not in its intended-position as where thepush rod 22A engages a notch incline 56 to move a diode slider its fulldistance, the protuberance 61 on that slider will open the main switch30M in passing during the central portion of its travel, with the samesequential operational result whenever the permutation of switches isbeing set or reset, whichever the case may be.

Thus, lighter,inexpensive switches rated for lesser current can be usedfor speed and diode switches 30 and 30D, and more closely grouped ifdesired to save space. The main switch 30M on the other hand, may beprovided with a heavier make and break current rating. Thus, greatlyimproved and less expensive switch unit is provided which has greatversatility.

The guide plate 31 maintains a predetermined close and constantrelationship between the push rods 22A and the conductors 38 whereby theswitches 30 may be operated with precision notwithstanding otherwisereasonably wide tolerances and springiness present in the cooperation ofthe sliders. Optimum operating cooperation for constancy of operationand results are accomplished in that the push rods 22A and guided switchconductors 38 interact not only on the speed switch sliders 32 and diodesliders 32D, but also upon the main switch sliders 32M with each guidedpush rod 22A movement. Relative play between the push rods and switchesis greatly minimized whether the sliders are conventional or unique formultiple functions in a time dimension. In fact, it will be observedthat regardless of the presence or absence of sequential operation ofthe switches, the switch blades 38 can be made much lighter at a savingof expensive bronze since the guide notches 43 provide the supportagainst displacement by the slider cams 50 which the heavier blades hadto withstand.

From the above description it will be observed that a versatilesimplified system is provided having a large selection of fixed speedsavailable for use with a set of selector push buttons for differentcontrol applications of the apparatus. The economy of co-wound fieldcoils that enables the wide selection without shorting any field turnsis appreciated and the economically designed switching construction withits permutation capabilities makes available a wide selection of speedsin many different speed ranges desired of the motor, and, in the desiredrange, utilizes at least twice as many fixed speeds as there are speedcontrol permutations available with the sliders in a multiple pushbutton switch. Additionally, the use of the half-wave rectifier on thelower speeds provides more torque than a resistance control of the fullwave AC potential at the same speed. Moreover, with space available,more speed control switches rated only for current carrying can beprovided at less cost than switches made for make and break operation.

The circuit shown in FIG. 5 is illustrative of the versatility of theswitch unit for 13 difierent fixed speeds out of 26 possible speeds.

The coils are all of the same length turns:

Coil Wire Gauge A No. 20 B No. 23 C No. 25 D No. 28 E No. 30

Armature A has 12 poles each having 44 turns of No. 28 gauge wire.Accordingly, the resistance of coil B is matched by the resistance ofCoils C, D and E connected in parallel for the highest speed, while theresistance of coil A in series with the diode, when used, drops thehighest diode speed below the lowest speed provided by all coilsserially connected under full wave potential.

With the circuit shown, seven fixed speed combinations can be had whichwith a diode doubles them to 14 combinations out of a mathematicalpossibility of 26.

Selecting six switches (2) to (7) marked X listed in the order of theirincreasing resistance it will be observed that only six of the switchesshown in the switch unit are devoted to coil selections by seven pushrod units 22A and the other, switches (l) and (8), are available for thediode and the main switch, respectively as described. When the diode isswitched into the circuit by opening switch (1), the coil alignment willinclude the coil A and the diode rectifier R ahead of the B coil for atotal of 14 fixed speeds.

The circuit is characterized by the three co-wound coils, D,C, and B ofdifferent wire sizes being connected by switches (2) and (6) in seriesin their order of diminishing sizes in a direction away from thearmature. The armature end X of the middle coil D is connected by twoconnections 81 and 85 including switches (6) and (4) respectively, tothe like ends X of the other coils C and E. The other like ends Y of thecoils, CD, and E are connected to the L side of the AC power linethrough switch (E), the outside connection 85 being directly and theother ends by two connections 87 and 89 including switches (3) and (7)respectively.

The circuit thus provided is an easy one to permute by the switcheswithout shorting any coils. The number of switches to operate anappliance are less than one-half the number of discrete control buttonsemployed to operate the circuit for the speed control of a series woundfield motor.

In this particular circuit, the timer 63 is driven by half wave currentthrough the diode 91 providing the continuous rectified current for thetimer at all times when the timer is used. A mechanical timer can beemployed which is started mechanically by the closing of the main switchor the setting of the timer but in the present disclosure the timer isconventional timer pulsed by the half wave to reciprocate a step ratchetfor measuring the time of motor energization.

It will be observed that additional novel relationships are present inthat three coils on their X side of the armature have their three leadends separately connected to the armature through switches 5437.

We claim: 1. A speed control for a universal electric motor connectedacross a source of alternating current comprising, an armature, v aplurality'of co-wound field coils on both sides of said armature havingdifi'ering impedances,

switch means for selectively connecting said field coil windings to saidsource in different permutations of series and parallel connections uponone side of the armature to change the impedance of the field coil turnswith respect to thearmature and to a predetermined number of lowimpedancefield coil windings on the other side of said armaturewith eachswitch position,

a half wave rectifier,

selective switch means to connect said rectifier in series relationshipwith said switches to vary the electrical potential impressed across thearmature, and

an additional field coil winding in series with said rectifier as a unittherewith to increase the effective impedance of said field coils.

2. The speed control called for in claim 1 in which said additionalfield coil winding is connected in series with said field coil windingson said other side of the armature, and

said selective switch means shunts said rectifier and additional fieldcoil winding.

3. A speed control for a universal electric motor connected across asource of alternating current comprising,

an armature,

a plurality of co-wound field coils magnetically effective on both sidesof said armature having differing impedances, switch means rated tocarry low current conducted by the coils for selectively connecting saidfield coil windings to said source in different permutations of seriesand parallel connections upon one side of the armature to change theimpedance of the field coil turns with respect to the armature and to apredetermined number of low impedance field coil windings on the otherside of said armature with each switch position,

a half wave rectifier an additional field coil winding in series withsaid rectifier as a unit therewith to increase the effective impedanceof said field coils, selective switch means to connect said rectifier inseries relationship with said switches to vary the electrical potentialimpressed across the armature, and

a timer operable from half wave pulse power connected in series withsaid half wave rectifier and said source of alternating current for amain run down when timer switch is opened before the main switch.

4. A speed control system for a universal electric motor connectableacross a source of alternating current comprising:

an armature,

a plurality of field coils of differing impedances disposed on.

one side of the armature, first selective switch means to connect thefield coils in series between the armature and one side of said source.second selective switch means to connect like ends of each coilindependently to said one side of said source for con necting at leasttwo of said coils in parallel, connector means having connectionsconnecting the other ends of said coils separately and to the armatureand including switches in at least two of said connections for selectingthe coils that will be connected in parallel between said armature andsaid one side of said source, and

field coil means including an additional coil and a rectifier seriallyconnected therewith as a unit and a switch shunting said rectifier andcoil.

5. A speed control for a universal electric motor connected across asource of alternating current comprising,

an armature,

a plurality'of cowound field coils on both sides of said armature havingdiffering impedances, and

switch means for selectively connecting said field coil windings to saidsource in difi'erent permutations of series and parallel connectionsupon one side of the armature to change the composite impedance of thefield coil turns with respect to the armature and to a predeterminednumber of low impedance field coil windings on the other side of saidarmature with each switch position,

a half wave rectifier,

selective switch means to connect said rectifier in series relationshipwith said switches to vary the electrical potential impressed across thearmature,

an additional field coil winding connected in series with said rectifieras a unit therewith to increase the effective impedance of said fieldcoils,

said permutating switch means being rated to conduct only the currentconsumed by said coils, and wherein additional switch means are providedserially connected between said field coils and said source forinterrupting current flow through said coils while said permutatingswitch means are switching said coils from one permutation to another.

6. The speed control described in claim 5 wherein said per mutatingswitch means comprise a multiple push button switch having a push buttonswitch and push button station for each permutation, and wherein saidadditional switch means interrupt said current upon actuation of one ormore of said push button stations.

1. A speed control for a universal electric motor connected across asource of alternating curreNt comprising, an armature, a plurality ofco-wound field coils on both sides of said armature having differingimpedances, switch means for selectively connecting said field coilwindings to said source in different permutations of series and parallelconnections upon one side of the armature to change the impedance of thefield coil turns with respect to the armature and to a predeterminednumber of low impedance field coil windings on the other side of saidarmature with each switch position, a half wave rectifier, selectiveswitch means to connect said rectifier in series relationship with saidswitches to vary the electrical potential impressed across the armature,and an additional field coil winding in series with said rectifier as aunit therewith to increase the effective impedance of said field coils.2. The speed control called for in claim 1 in which said additionalfield coil winding is connected in series with said field coil windingson said other side of the armature, and said selective switch meansshunts said rectifier and additional field coil winding.
 3. A speedcontrol for a universal electric motor connected across a source ofalternating current comprising, an armature, a plurality of co-woundfield coils magnetically effective on both sides of said armature havingdiffering impedances, switch means rated to carry low current conductedby the coils for selectively connecting said field coil windings to saidsource in different permutations of series and parallel connections uponone side of the armature to change the impedance of the field coil turnswith respect to the armature and to a predetermined number of lowimpedance field coil windings on the other side of said armature witheach switch position, a half wave rectifier an additional field coilwinding in series with said rectifier as a unit therewith to increasethe effective impedance of said field coils, selective switch means toconnect said rectifier in series relationship with said switches to varythe electrical potential impressed across the armature, and a timeroperable from half wave pulse power connected in series with said halfwave rectifier and said source of alternating current for a main rundown when timer switch is opened before the main switch.
 4. A speedcontrol system for a universal electric motor connectable across asource of alternating current comprising: an armature, a plurality offield coils of differing impedances disposed on one side of thearmature, first selective switch means to connect the field coils inseries between the armature and one side of said source, secondselective switch means to connect like ends of each coil independentlyto said one side of said source for connecting at least two of saidcoils in parallel, connector means having connections connecting theother ends of said coils separately and to the armature and includingswitches in at least two of said connections for selecting the coilsthat will be connected in parallel between said armature and said oneside of said source, and field coil means including an additional coiland a rectifier serially connected therewith as a unit and a switchshunting said rectifier and coil.
 5. A speed control for a universalelectric motor connected across a source of alternating currentcomprising, an armature, a plurality of co-wound field coils on bothsides of said armature having differing impedances, and switch means forselectively connecting said field coil windings to said source indifferent permutations of series and parallel connections upon one sideof the armature to change the composite impedance of the field coilturns with respect to the armature and to a predetermined number of lowimpedance field coil windings on the other side of said armature witheach switch position, a half wave rectifier, selective switch means toconnect said rectifier in series relationship with saiD switches to varythe electrical potential impressed across the armature, an additionalfield coil winding connected in series with said rectifier as a unittherewith to increase the effective impedance of said field coils, saidpermutating switch means being rated to conduct only the currentconsumed by said coils, and wherein additional switch means are providedserially connected between said field coils and said source forinterrupting current flow through said coils while said permutatingswitch means are switching said coils from one permutation to another.6. The speed control described in claim 5 wherein said permutatingswitch means comprise a multiple push button switch having a push buttonswitch and push button station for each permutation, and wherein saidadditional switch means interrupt said current upon actuation of one ormore of said push button stations.